Wahoo Kickr Core Help

Hi all,

First and foremost, I’m not a cyclist so please treat me as someone with little basic knowledge.

In short, have been using the HR2VP app with an HR strap and cadence sensor on my spin bike. Whilst ok, its just limited. But has proved to me that I’d enjoy Zwift long term. So…

Decided to go ahead and get a smart trainer (Wahoo Kickr Core). But a bit confused. It comes with a Shimano 11 speed cassette. That means very little to me till I read up before ordering.

The bike I have is a mountain bike with a 6 speed cassette.

Without any knowledge - surely I connect up a 6 speed to the 11 speed and away I go. Apparently not.

So the reason for the post is to ask what I need.

Here is my kid’s 10 speed cassette.

So… would my mountain bike work with a Kickr, or do I need to match up the cassette. If I do that, then would my 9 year old son by able to then whip off his back wheel and use his 10 speed cassette.

Or do I need a 6 speed cassette for my mountain bike and then a separate 10 speed cassette for my son’s bike?

If my mountain bike is not suitable, why not? Do I need a new bike? Do all 11 speed cassettes match, or do teeth on smallest and largest cogs make a difference?

As I say, I’m a newbie, I do like Zwift and want to do races primarily, but also some workouts at times too - but mainly racing. I’m likely a Cat D rider.

What I’m most worried about is buying the Kickr Core at £600, then finding I need a new £350 bike. The £600 is a huge expense for, what will be, a hobby to keep fit. I just dont want any hidden costs, mistakes etc.

It’s a little hard to tell from the picture with the wheel installed in the bike, but I think you might have a 6 speed freewheel, not a cassette. A freewheel can’t be installed on the trainer, and 6 speed cassettes are not common.

Your 6 speed drivetrain will not work with an 11 speed cassette and it would not be cost effective to change the drivetrain of your bike to 10 or 11 speed, especially if it uses a threaded freewheel instead of a cassette. The spacing between cogs is the same on all 11 speed cassettes, although the cog sizes may differ and that can affect chain length requirements.

Your son’s bike has an Altus rear derailleur, and I don’t think Altus comes in 10 speed - you may want to double check your count of the rear cogs. It’s not impossible to use an Altus rear derailleur with a 10 speed shifter, but they don’t generally come that way from the factory.

If you want to keep the Kickr core, probably the best solution would be to make sure you understand the number of cogs on your son’s bike (hopefully it’s at least 8 for ease of installing a cassette on the trainer). Then buy a cassette for the Kickr with that number of cogs (preferably where the largest cog has the same number of teeth so you don’t have to worry about chain length) and get a new or used bike for yourself that matches the number of cogs on your son’s bike. Then you would be able to use either bike on the trainer without modifications.

Sorry, you are right. Its 8, not 10 on my son’s bike. Not only am I a person of little knowledge, but also cant count.

So are you saying that, for me, I ultimately need a new bike and then buy a cassette for the trainer to match the cassette AND cogs? (assume ideally the exact same cassette?)

And if I dont match to my son’s then I have to have a 2nd cassette to use on the trainer for my sons bike?

Yes, the ideal solution would be to have an 8 speed bike for yourself, and an additional 8 speed cassette for the trainer. The largest cog on the trainer’s cassette should preferably not be larger than the largest cog on the rear wheel of any bike you plan to use on the trainer.

As a side note to this, I have a spin bike with magnetic resistance. Would power pedals be a reasonable option?

Yes assuming the spin bike uses 9/16" thread pedals. Most do, but some are 1/2". However the price of power pedals will probably not be very different from the price of a used 8 speed bike, especially if you sell your 6 speed bike.

Yes. 7 and 8 speed cog thickness+spacing are not hugely different so that sometimes works sort of OK, but it won’t be perfect and may require fussy adjustment. You will not want to swap the cassette on the trainer frequently. It would probably get in the way of your desire to ride.

I was thinking power pedals instead of new bike and kickr. Anyone can jump on spin bike and ride vs different bikes, cassettes, changing them over etc.

£350 pedals vs £600 trainer. But auto resistance vs changing manually. Do I lose much else? Will I regret not getting the trainer? Or will pedals let me race fairly and feel “connected and immersed”?

Thanks so far Paul.

Good point. Another thing to consider is that Zwift are launching their Hub smart trainer (£449 with cassette of your choice - you could order it with an 8 speed cassette installed). Then if you can find a used 8 speed bike for yourself, that would not be very different from the price of the Kickr.

You read my mind. Yes, thats also another option. I was enjoying the HR2VP app which uses heart rate + cadence to generate power. All was going well, enjoying it. Then did a race yesterday (Pretzelfest 70km). And it just felt too slow to react to me working harder or lighter. Did a HUGE effort up the mountain, came down and got onto flat. But cos I had rested coming down the hill my HR had dropped to 110bpm (vs 130bpm when I ride on flat after a few km). So, I ended up pedalling a bit faster to catch a group but power hardly changed (cos my HR stayed the same and, due to the mountain effort, probably felt I was doing very little).

So… with that in mind would power pedals (lets say £300) end up being accurate enough or would I be forever thinking “did I turn up the resistance enough for that hill” or “did I turn it up too much and power pedals didnt know I was working as hard as I was”? Or are they extremely accurate in my sat on saddle, stood up on pedals, pushing harder etc.

At this point am I just going to think “why didnt I get the smart trainer”?

But, if I’m learning correctly, I’d need to find an 8 speed bike that has the same number of cogs / teeth as the cassette that comes with the Zwift hub?

This seems like most sensible low cost option.

Just a point/question on matching 6 speed bike with 8 or 11 speed cassette. Isn’t it possible with the right sized chain (8 or 11 speed) to just use 6 or 8 of the cassette cogs?

I had a very old (35yrs plus) bike which ended up as 8 speed. I didn’t want to spend much on bike so when my Neo 2 came (second hand £500) with an 11 speed cog all I did was put an 11 speed chain on my bike (which I no longer ride outdoors) and set the gear select system to not go near top one and bottom two cogs. Must add that I didn’t have index linked gear system so changing gear maybe only possible because of cable movement rather than indexing?

It will probably work fine if the large cog on the rear wheel of the bike is larger than the large cog on the trainer. If the chain is a little bit slack it should still be OK. I’m not sure what Zwift are offering for 8 speed gearing but you can probably find out before buying.

So out of these options, what would you go for?

Existing spin bike with Assioma Uno Single-Sided Power Meter Pedals (£350).

Or new bike (2nd hand or new - lets say £200) then (assuming cogs match):

Zwift Hub + cassette £450
Kickr Core + cassette £650

Ultimately, would I be “stupid” to go down the pedal route because Zwift, RGT gives feedback to smart trainers. Or for someone who wants to race fairly (so if I go uphill I want to feel the hill, if I go up a mountain my legs should burn, when I go downhill I can rest) will pedals plus manual resistance be sufficient?

My worry is due to the cost. If we were saying £80 pedals or £160 trainer then the issue is minimal. But £600 is a huge commitment to then find out I need a new bike, new cassette, extra cost, wrong bike etc… its scary for someone who takes a careful approach to purchases.

Using a smart trainer will give you a much better experience, because the terrain (e.g. gradient) will feel a lot more realistic.

To use those pedals you’ll also need cycling shoes with the Look 3-bolt cleat format

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Oh… thats another cost :slight_smile:
I might go back to running outdoors. Seems simpler ha ha.

So… my missus was wanting a new mountain bike (that I may end up sharing). Looking at a "Carrera Karkinos) which says “The Karkinos comes equipped with a bigger 8-speed cassette at the back wheel”.

So under this premise, am I right in saying the back wheel is easy to remove (quick release), drop it onto Zwift Hub or Kickr Core with an 8 speed cassette installed (would I have to also ensure number of teeth on upper and lowest cogs match?) and be good to go?

Is removing and connecting up the bike a problem in any way (eg breaks the trainer, means calibration is off) or is it “plug n play” so to speak. Just drop it on the installed cassette and away I go?

Missus is nervous that removing back wheel constantly (well, when she goes out on the bike and then when I want to ride indoors) will break either the bike or the trainer.

Would this bike (a cost we are committed to anyway) + Zwift Hub or Kickr Core be the best way to go?

Removing the wheel and putting the bike on the trainer will not harm the equipment.

A “bigger” 8 speed cassette probably has a larger rear cog than you’d get with the Zwift Hub trainer, so it should be fine. If you buy a cassette you may as well get one with the same gearing as the bike, but a smaller large cog on the trainer should be OK as long as it’s not vastly smaller. The size of the small cog does not matter.

When you say same gearing, do you mean the same number of teeth on the large and small cogs?

Sorry for the number of questions, and what may be simpleton ones, but has helped a lot.